They can be caused by environmental allergies, which typically can be treated with a range of things, from removing known allergens from the environment to antihistamines and supplements to immunotherapy or immunosuppression, depending on the allergic reaction and the pet.
Atopy (also referred to as “atopic dermatitis” and previously known as “allergic inhalant dermatitis”) is a common canine and feline condition in which allergens present in the environment effect an allergic reaction in the skin. It is one of several known causes of allergic skin disease, a common umbrella term for a group of allergies that manifest in the skin.
Atopy is believed to happen when certain proteins present in the environment are taken into the body through inhalation or direct contact with the skin. When they precipitate an allergic response, these proteins are referred to as allergens. When the allergic response happens in the skin, the result is almost always an inflammation of the skin we refer to as “allergic dermatitis.”
Common allergens include pollen (from grasses, trees, and weeds), mold spores, house dust/house dust mite proteins, insect proteins, and other miscellaneous proteins that may also come from human skin or natural fibers, for example. Atopic animals will display highly individualized responses to one or more environmental allergens.
A genetic basis is well understood to underlie atopic dermatitis in dogs, but this has not been proven in cats. In both species, other factors including geography (regional pollens and plants), the presence of other allergens (like fleas) and endocrine diseases (like thyroid disease in dogs) — can worsen, mimic, and/or underlie atopic disease.
Animals with atopy become very itchy; the resultant scratching leads to skin injuries and secondary skin infections. Atopy is usually first noticed in dogs and cats younger than 3 years of age, although older pets can also be affected. Unfortunately, pets that develop atopy are usually plagued by skin problems throughout their lives.
Atopic dermatitis is characterized by the variable presence of itching, redness, pustules (infected pimples), wheals (like hives), and crusts. The face, legs, feet, ventrum (belly, underarms, and groin), and ears are most often affected, but no area of the body is off limits. In dogs, ear infections are very commonly associated with atopy.
Cats usually display signs of excessive licking in a symmetrical pattern (on the belly, back, and behind the legs is most common) and/or they can develop tiny scabs around the neck, tail base, or elsewhere on the body.
A more comprehensive list of signs in dogs and cats includes:
A hallmark of atopic dermatitis is that signs tend to be seasonal and tend to wax and wane in severity. However, pets that are allergic to house dust mites or other indoor allergens can have year-round problems, because exposure to indoor allergens is not dependent on season of the year.
Most pets are diagnosed based on signs, history, and response to treatments, but getting to a definitive diagnosis can be a complicated affair. Given that every affected animal suffers a highly individualized version of the disease, determining what an animal is allergic to may require intradermal (skin) testing and/or serum testing (blood testing).
Intradermal skin testing can sometimes be performed at your veterinarian’s office. However, because the allergens used for this test are very specific (they vary depending on your region of the country), your veterinarian may refer you to a veterinary dermatologist.
Usually, an area of fur is shaved from your pet to expose enough skin to perform the test. Tiny amounts of each test allergen are injected using very small needles just under your pet’s skin in different areas. After a brief waiting period, your veterinarian will examine the injection sites to measure the degree of local allergic response (redness or a small hive). Allergens that your pet is not allergic to will not cause a reaction, and allergens that your pet is allergic to will cause a reaction that corresponds to the severity of the allergy. Pets are monitored carefully during the procedure in case a serious reaction occurs and treatment is required.
The other type of allergy testing, serum allergy testing, is becoming more popular. The test is performed at a laboratory using a small blood sample taken from your pet so that your veterinarian does not need to shave your pet or have special allergens on hand. As with intradermal skin testing, the results of serum allergy testing can reveal which allergens are not causing an allergic reaction in your pet, which ones are causing a mild reaction, and which ones are causing a more serious reaction.
Depending on which type of allergy test is performed, you may need to discontinue your pet’s allergy medications before the test. Otherwise, the test results may be affected. Your veterinarian will tell you which medications can be used and which ones may need to be discontinued.
Any breed of cat or dog may be affected by atopy, but in dogs it is most prevalent among Boston Terriers, Boxers, most Bulldog breeds (particularly English Bulldogs), Cairn Terriers, Sharpeis, Dalmatians, English Setters, Golden Retrievers, Irish setters, Labrador Retrievers, Lhasa Apsos, Miniature Poodles, Miniature Schnauzers, Pugs, Scottish Terriers, West Highland White Terriers, and Wire-Haired Fox Terriers.
Four categories of treatment have been described. They comprise:
Many of the therapies described here can be used to control atopy over the long term. Avoidance of problem allergens may be the best way to prevent flare-ups for dogs and cats with atopy.